Question

If the $n-th$ term of an A.P. $=7n+4,$ then $S_n=\frac{n}{2}(7n+15)$.

• A. True
• B. False

Answer 1

The correct option is A True

Here $a_n=7n+4$
$\Rightarrow a_1=7\left(1\right)+4=11$
Now, $S_n=\frac{n}{2}(a_1+a_n)=\frac{n}{2}(11+7n+4)$
$\Rightarrow S_n=\frac{n}{2}(7n+15)$